Enlarged end flanges are commonly provided on the ends of fluid-conveying pipes for the purpose of enabling the pipe to be sealed with respect to, and to be secured mechanically to, a fitting in a pump, valve, or other fluid circuit element. Conventionally, a pipe-nut fits loosely over the pipe, and engages a screw-thread formed in the circuit element, whereby the flange on the pipe may be drawn tightly into the fitting.
In the case where the enlarged end flange on a pipe involves only a slight change in diameter, the conventional manner of providing the flange is to flare the end of the pipe. In flaring, the pipe is gripped or clamped radially, and a tool is inserted axially into the end of the pipe. Pressing the tool into the pipe serves to cause an enlargement of the end of the pipe. That the thrust is axially-directed is a characteristic of flaring. When only a slight swelling is called for, the flaring can be made with quite crude tools and processes.
One of the difficulties in flaring the end of a pipe arises when large changes in diameter are called for. As the diametral change becomes larger, it becomes increasingly difficult to control the bending and distortion of the flange, by means of the axially moving punch or tool. The designer knows that if he calls for too much of a diamteral change, the metal of the pipe wall tends to pucker, crumple, and otherwise take on unwanted deformations. The material may even crack or split.
Accordingly, when large changes of diameter have been required, it has hitherto usually been the case that a separate component is manufactured, and the separate component is then secured, by brazing or soldering for example, to the end of the pipe. Whilst the use of a separate component releases the designer from many constraints, of course the separate component adds greatly to the expense of the finished pipe.
It is an aim of the invention to provide an enlarged flange on the end of a pipe, in which the diametral enlargement is greater than has hitherto been considered safe, and yet in which that large degree of diametral enlargement is controllable, and does not lead to spurious deformations of the pipe material.